Activation of receptors for endogenous excitatory amino acids have been shown to bring about an increase in cGMP formation in cerebellum. We have now characterized the cGMP response to various excitatory decarboxylic amino acids in 8 day old primary cultures of rat cerebellar granule cells. A specific increase in cGMP content following the addition of kainic acid to the cultures has been found. This observation will be a departing point to study interactions among kainic acid, aspartates, and glutamate recognition sites at the cellular level, and to characterize whether kainic acid receptors have a physiological role or participate in neurodegenerative disorders.